Well-established power distribution systems exist throughout most of the United States, and other countries, that provide power to customers via power lines. With some modification, the infrastructure of the existing power distribution systems can be used to provide data communication in addition to power delivery, thereby forming a power line communication system (PLCS). In other words, existing power lines that already have been run to many homes and offices can be used to carry data signals to and from the homes and offices. These data signals are communicated on and off the power lines at various points in the power distribution communication system, such as, for example, near homes, offices, Internet service providers, and the like.
While the concept may sound simple, there are many challenges to overcome in order to use power lines for data communication. Power distribution systems include numerous sections, which transmit power at different voltages. The transition from one section to another typically is accomplished with a transformer. The sections of the power line distribution system that are connected to the customers typically are low voltage (LV) sections having a voltage between 100 volts and 240 volts, depending on the system. In the United States, the low voltage section typically is about 120 volts (120V). The sections of the power distribution system that provide the power to the low voltage sections are referred to as the medium voltage (MV) sections. The voltage of the MV section is in the range of 1,000 Volts to 100,000 volts and typically 8.66 kilo volts (kV) to neutral (15 kV between phase conductors). The transition from the MV section to the LV section of the power distribution system typically is accomplished with a distribution transformer, which converts the higher voltage of the MV section to the lower voltage of the LV section.
Power system transformers are one obstacle to using MV or LV power distribution lines for data communication. Transformers designed for conversion of voltages at power frequencies (i.e. 50 or 60 Hz) present complex and often undesirable series and shunt impedances that can be detrimental to data signal frequencies useful for data communication. As such, power distribution communication systems face the challenge of passing the data signals around (or sometimes through) the distribution transformers.
Many power lines, including both LV (external and the internal customer premise power line wiring) and MV power lines, provide a high impedance communication channel for high frequency data signals thereby significantly attenuating data signals. In addition, power lines may provide a very noisy communication channel and such noise is often sporadic and unpredictable. Thus, due to the limited power that may be used to transmit data signals on power lines (for example, due to Federal Communication Commission (FCC) regulations regarding RF emissions), high frequency data signals will only propagate a finite distance that in some instances may not be far enough from the transmitting source to be reliably received by the intended communication device.
Thus, there is a need for a power line communication device to extend the range of communications of a power line communication (PLC) device. Such a device should be designed to facilitate bi-directional communication. In addition, the device (or repeater as sometimes referred to herein) should enable the transmission and reception of broadband radio frequency (RF) signals used for data transmission over high voltage (HV), MV and LV power lines, including the internal customer premise wiring. Finally, it is desirable to design such a repeater to be installed without the need to disconnect power from the power lines.